Posted 2006-03-27 8:20 AM (#39581) Subject: A question for Reg
Veteran
Posts: 198 Location: Iowa
Reg,
Considering that you're the resident Einstein on trailer weights, etc. I was hoping you could help me answer a question.
I have an 18' Cornpro stock gooseneck trailer. Even with the gooseneck adjusted all the way down, it is slants up 2.5" higher at front of the trailer box than at rear of trailer box....or, about half a bubble off on a level. With the trailer set up this way, I only have 5" clearance between neckover and truck bed rails...not much, and I have already scraped it once.
The trailer has six bolt axles and 15" tires. I can go to 16" tires, but would need new rims also.
Would this do much to solve my problem. The 16" tires are 2 inches bigger in diameter, so would give me 1" additional height at back of trailer. Using your formula, about how much would this translate into additional extension of the gooseneck tube for more clearance? And would it be worth it? Getting 16" rims and tires is about $350 more than just getting new 15" tires...I don't mind spending the money, but if it won't make much difference at the gooseneck hitch, I don't want to waste my money. Just looking for your very educated opinion here. I don't want to lift the trailer, because it's an older trailer and not worth the investment. I could also just jack the gooseneck up another couple of inches...but then the trailer would be about 4 inches higher in front than in back...don't know if that would be safe/smart.
Posted 2006-03-27 8:54 AM (#39583 - in reply to #39581) Subject: RE: A question for Reg
Expert
Posts: 2689
Originally written by Flooper on 2006-03-27 9:20 AM
Reg,
Considering that you're the resident Einstein on trailer weights, etc. I was hoping you could help me answer a question.
I have an 18' Cornpro stock gooseneck trailer. Even with the gooseneck adjusted all the way down, it is slants up 2.5" higher at front of the trailer box than at rear of trailer box....or, about half a bubble off on a level. With the trailer set up this way, I only have 5" clearance between neckover and truck bed rails...not much, and I have already scraped it once.
The trailer has six bolt axles and 15" tires. I can go to 16" tires, but would need new rims also.
Would this do much to solve my problem. The 16" tires are 2 inches bigger in diameter, so would give me 1" additional height at back of trailer. Using your formula, about how much would this translate into additional extension of the gooseneck tube for more clearance? And would it be worth it? Getting 16" rims and tires is about $350 more than just getting new 15" tires...I don't mind spending the money, but if it won't make much difference at the gooseneck hitch, I don't want to waste my money. Just looking for your very educated opinion here. I don't want to lift the trailer, because it's an older trailer and not worth the investment. I could also just jack the gooseneck up another couple of inches...but then the trailer would be about 4 inches higher in front than in back...don't know if that would be safe/smart.
Thanks.
Flattery will get you.... Oh, just about ANYTHING ! (-:
Two quick answers for you, make that 3:
a) 2 1/2 inches is not very much, if there isn't a difference in tire temperature it probably isn't worth messing with. To put this another way, your suspension can probably absorb such a small difference.
b) I can't do the arithmetic without knowing the coupler to halfway between the front and rear axle measurement.
c) Another indication is whether or not your front brakes lock up "early", e.g. before you get enough braking - this would indicate that you need to get some more of the load onto the front axle.
I see so many trailers running around "nose high" that sometimes I think we worry too much. Although you say it is an 18ft trailer that doesn't give me much of an idea how far it is between the coupler and the effective pivot point of the rear axles. As a ROUGH guess halfway between the two rear axles is where your trailer pivots when lifted from the coupler. You can think of this as a "wheelbarrow model" if you like.
If you measure from the coupler to half way between your axles - call that "X", then for every inch you raise the trailer at the coupler you will change the pitch of the trailer by 1/X. Compare that to the 3ft or so between your axle centers to figure the effect on the tires/wheels.
REMEMBER !!! Rims are measured by DIAMETER and only HALF of that affects axle height, so going from a 15 to a 16 rim only raises the axle 1/2 inch. TIRES (or tyres) are measures by Diameter, WIDTH and profile. The HEIGHT that each cm of additional width adds is the profile's percentage of a cm, e.g. 7.5mm for a STxxx/75R1x tire.
Summary, if your tires are running at the same temperature and the brakes are balanced - find a better spending opportunity for that money.
Posted 2006-03-27 10:12 AM (#39589 - in reply to #39581) Subject: RE: A question for Reg
Veteran
Posts: 198 Location: Iowa
Perfect Reg!! Thanks a bunch. I'll measure the distance and use your formula. But I'm leaning towards staying with the 15" tires, since it does't look like the 16" tires will get me all that much more clearance, and the trailer doesn't have that much of a nose-high attitude anyway. Thanks for all your help...I could never have figured out how to figure it out on my own!!!
Posted 2006-03-30 10:00 AM (#39781 - in reply to #39581) Subject: RE: A question for Reg
Elite Veteran
Posts: 720
Just a thought. If it has spring axles, they'll equalize at most any degree of level. Torsion axles need to be relatively level in order for each one to carry it's share of weight & braking. So- if it has springs, run it unlevel. Torsion, be more careful.
A question for Reg
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